RU2306527C2 - Method for changing distance on basis of polarization properties of photon echo - Google Patents

Abstract

FIELD: measuring equipment engineering, possible use for recording distance between large-dimension objects of engineering structures.

SUBSTANCE: in accordance to the invention, support laser impulse and probing laser impulse are directed into resonance environment. In resonance environment, photon echo signal is formed. Angle of rotation of photon signal polarization vector, appearing during influence of longitudinal magnetic field on resonance environment, is recorded. The angle depends on time interval between exciting support and probing impulses, on intensity of applied magnetic field, on the type of enabled quantum transition. On basis of value of recorded angle, time interval, dividing support and probing impulses, is determined. Time interval is converted to the value of the distance being measured.

EFFECT: increased speed of operation, production of absolute value of the distance being measured.

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Description

The invention relates to measuring technique and can be used to measure the distance between large-sized objects of engineering structures, for example, radio telescopes and radio engineering complexes with antennas of various shapes and sizes, aircraft and shipbuilding equipment, optical paths of laser systems, linear and ring accelerators.

The known principle of the pulsed method of measuring distances, based on the determination of the travel time of the pulse from the transmitter to the reflector and inversely proportional to the double measured distance (Kamen X. Electronic measurement methods in geodesy. M .: "Nedra", 1982, pp. 104-105).

The disadvantage of the principle is the low accuracy of measuring distances due to the use of an electronic method of recording the time interval between the reference and probing pulses.

A device is known that is an example of the implementation of a method for recording distances based on a change in the direction of the linear linear polarization of light under the influence of an external modulating microwave field (Gyunashyan KS, Papayan VK, etc. High-precision electro-optical range finder DVSD-1200. - Geodesy and cartography , 1973, No. 9, p. 14-18).

The disadvantage of this method is the low speed and the inability to determine the number of integer wavelengths of microwave modulation that fit within the measured distance, and registration is only the Domer (part of the wavelength of microwave modulation of the process of rotation of the polarization of light, corresponding to the last incomplete period of modulation) of the portion of the measured distance that does not correspond microwave wavelength value.

The present invention is to increase the speed and accuracy of distance measurement. This is ensured by using the polarization properties of the signal of the primary or stimulated photon echo (PE), based on the effect of the non-Faraday rotation of its polarization vector [I.V. Evseev, V.M. Ermachenko, V.V. Samartsev. Depolarizing collisions in nonlinear electrodynamics. - M .: Nauka, 1992. S. 28-39, 75-78]. The measurement of the distance based on the polarization properties of the FE (photon echo) consists in directing the reference laser pulse and the probe laser pulse, which passed through the measured distance, into the resonance medium in which the PE signal is generated under the influence of a sequence of reference and probe laser pulses. Then determine the angle of rotation of the polarization vector of the PV arising from the action of a longitudinal magnetic field on the resonant medium. This angle depends on the time interval between the exciting reference and probe pulses, on the strength of the applied magnetic field, on the type of quantum transition involved, and does not depend on the path length traveled in the resonant medium by the exciting laser pulses and the PV signal. In this case, the resonant medium has an optical phase memory containing information on the angle of rotation of the polarization vector of the PV and, accordingly, on the determined time interval between the reference and exciting pulses. The magnitude of this recorded angle determines the time interval separating the reference and probe pulses. Next, recalculate the time interval in the size of the measured distance.

The existing Faraday rotation of the polarization vector of optical pulses is 3-4 orders of magnitude smaller than the non-Faraday rotation of the polarization vector of the echo signal. The sensitivity of the recorder does not allow to register the Faraday rotation of the polarization vector of optical pulses, but provides registration of the non-Faraday rotation of the polarization vector of the PV signal.

The proposed method for measuring distances based on the non-Faraday rotation of the PV polarization vector is illustrated in the drawing, which shows a diagram for measuring the distance between objects 1 and 2. There is a source of a sequence of laser pulses 1 spaced in time with specified intensities and time parameters (durations of the reference and probe pulses and the time interval between them), a Glan polarization prism 2, a Cornu prism 18, an angular reflector 7 on a support mounted on object 2, a swivel mirror 17, a cuvette with a resonant medium 15, mounted inside the solenoid 4, diaphragms 9, 19, 20, the output polarizing prism of Glan 8, used to decompose the echo signal into two components with orthogonally oriented directions of linear polarization vectors, the first and second channels of recording component components an echo signal consisting of photorecorders 10, 11 and converters 12, 13, processor 14.

The distance measurement is as follows. The laser pulse source 1 generates a light pulse, which arrives at the Glan polarization prism 2, while part of the radiation (reference laser pulse 6) with the vertical direction of the polarization vector passes in the forward direction through the cell 15 with the resonant medium located in the longitudinal magnetic field of the solenoid 4, created by current from a program-controlled current source 3, and the other part (probing laser pulse 5) enters the rotary mirror 17 and, reflected from it, goes through the diaphragm 19 to the measured dist It is reflected from the corner reflector 7 and, having passed the measured distance in the opposite direction, through the diaphragm 20 enters the cell 15 at an angle α to the propagation direction in the cell of the reference pulse. The diaphragms 19 and 20 ensure that the probe pulse enters the centers of the working planes of the corner reflector 7, which is achieved by rotating the optical echo-range finder (OED) relative to the axis of its mounting on the base and relative to the corner reflector until the center of the probe pulse arriving from the distance coincides with the center of the diaphragm 20. Under by the action of the reference and probing pulses in the resonant medium, a FE signal is formed, propagating at an angle α to the direction of propagation of the probe pulse and at an angle 2α to n Distribution board reference pulse. In this case, the FE signal under the influence of a longitudinal uniform magnetic field experiences a rotation of the polarization vector by an angle φ and after passing through the diaphragm 9, which does not pass exciting pulses, passing the output polarizing prism of Glan 8, decomposes into two components with orthogonally oriented directions of linear polarization vectors (vertical and horizontal directions of linear polarization vectors). Each of the components of the echo signal is recorded by the photo recorders 10 and 11, the signals from which are fed to the corresponding information converters 12 and 13, and then fed to the two inputs of the processor 14. In the processor, the angle is determined from the ratio of digital codes corresponding to the intensities of the echo signal

where I _{e (x)} is the component of the echo signal with the horizontal direction of the polarization vector, k is the correction factor, showing how many times the readings of the measured value in the first channel differ in relation to the readings in the second channel

where k _PMT1 is the gain of the photorecorder 10 (photoelectronic multiplier) in the first channel, k _PMT2 is the gain of the photorecorder 10 (photoelectric multiplier) in the second channel. The dependence of the intensity of the PV signal on the angle α between the exciting pulses does not affect the value of ***, because the coefficient of exponential decay of the FE with increasing angle α equally affects the values found in the numerator and denominator of formula (1). Then from the well-known in the scientific literature [Alekseev A.I., Evseev I.V. Photon echo in a gas in the presence of a magnetic field. - JETP. - 1969. - T.57. - No. 11. - S.1735-1744] expressions

ε_a,b=μ₀g_a,bH, μ₀ - ядерный магнетон, Н - напряженность продольного магнитного поля, g_a,b - гиромагнитное отношение основного а и возбужденного b уровней соответственно, определяется временной интервал между опорным и зондирующим импульсамиWhere

ε _{a, b} = μ ₀ g _{a, b} H, μ ₀ is the nuclear magneton, H is the longitudinal magnetic field strength, g _{a, b} are the gyromagnetic ratios of the main a and excited b levels, respectively, the time interval between the reference and probe pulses is determined

Next, the time interval τ ₁₂ , taking into account the refractive index of light n in the propagation medium of the probe pulse, determined by measuring temperature, humidity and pressure at the measured distance, is converted into the distance traveled by it minus the distance between the Glan prism 2 of the PV formation point:

where c is the speed of light.

The value of the measured distance will be equal to the difference of the entire path traveled by the probe pulse and the path traveled by it inside the OED (ΔS):

where ΔS is the instrumental correction of the OED.

Three factors affect the instrumental correction AS OED: the difference in the path length traveled by the reference pulse from the Glan prism 2 to the resonant medium and the path length traveled by the probe pulse from the OED input (from diaphragm 20) to the resonant medium; the path length of the probe pulse in the area between the Glan prism 2 and the diaphragm 19; the distance between the centers of the working surfaces of the corner reflector. In this case, the zero mark of the OED is located on the plane of the diaphragms 19 and 20. The instrumental correction is determined experimentally during the metrological verification of the OED.

Claims (1)

A method of measuring distance based on the polarization properties of a photomultiplier (photon echo), characterized in that they direct the reference laser pulse and the probe laser pulse passing through the measured distance to the resonant medium, form a photomultiplier signal in the resonant medium under the influence of a sequence of reference and probe laser pulses, record the angle of rotation of the polarization vector of the FE, which occurs when a longitudinal magnetic field is applied to the resonant medium, which depends on the time interval between the by fading reference and probe pulses, on the strength of the applied magnetic field, on the type of quantum transition involved, and does not depend on the path length traveled in the resonant medium by exciting laser pulses and a PV signal having optical phase memory containing information on the angle of rotation of the polarization vector of the PV and , respectively, about the determined time interval between the reference and exciting pulses, and the time interval dividing orny and probe pulses produce more recalculation time interval to the value of the measured distance.